Authorities in the fields of physiology and clinical medicine have long recognized that an acceptable substitute for whole blood is needed. Recurrent shortages, adverse reactions, costs and the problems of storage are among the reasons which make a whole blood substitute a necessity. The need for a satisfactory substitute for hema-atocrit has been similarly recognized.
In the prior art, a number of compositions, i.e.: Lactated Ringer's Solution, Dextran, Modified Gelatin, Hydroethyl Starch, Fluorocarbons, Perfluorocarbons and Polyvinylpyrrolidones are referred to as "blood substitutes". Reference: Chemical Abstracts, 8th Collective Index, 1972 The scientific literature however, contains no evidence that any of these or any other known substance can function as a whole blood substitute or that they are conventionally used as such. The compositions referred to above are employed in one of two restricted ways: to expand plasma volume or to enhance oxygen transport.
Aside from their limited physiological function, the use of "blood substitutes" is highly restricted because of other shortcomings and the fact that some of the cited compositions have been associated with adverse reactions. Thus, an example of a common and serious shortcoming of available "blood substitutes" is the short period of time they are able to carry out the physiological function ascribed to them. Other reported difficulties associated with the compositions cited above follow: